What are orcs' favorite flavors of pie, and how does pie flavor affect the effectiveness of their defense of said pie?

Why a completely new game system for Numenera, rather than create a campaign setting to leverage you existing published work for Arcana Unearthed and the like?

Given the number of varying games with differing mechanics on the market, what's unique about the mechanics of Numenera that should encourage me to try it, versus spending the same dollars on material that supports a game I already know how to play?

"The Soul of D&D?It's rolling a natural 20 when you're down to 3 hit points and the cleric's on the floor and you're staring that sunnavabitch bugbear right in his bloodshot eye and holding the line just long enough to let the wizard unleash a fireball at the guards who are on their way, because they're all that stands between you, the Foozle and Glory." - WizarDru

Monte, What are you feelings on d20 as a system? My group of gamers has tried a variety of systems, d10 white wolf, d6 shadowrun, along with other games like TROS, burning wheel, and Warhammer Fantasy (3rd ed). My feelings are that the linearity of d20 works well with heroic adventure, but is poor for games that want more simulation. While D&D has always been heroic adventure (and 4th ed more so than others) there always seems to be a strong nod toward simulation. Do you think that d20 systems and D&D can create a gritty realistic setting that's as satisfying to players as a more granular resolution system like you get with rolling multiple dice toward a target number?

What are the major mistakes you think designers should avoid? What are you thoughts about the current atmosphere regarding play and design? If you could only suggest three reference books for world building, what would they be?